Add nginx.ingress.kubernetes.io/add-header annotation

[danielnginx]

Add nginx.ingress.kubernetes.io/add-header annotation

[pdabelf5]

for request headers we have this annotation already nginx.org/proxy-set-headers. It would be great if we could keep it consistent where we can add multiple response headers similar to https://docs.nginx.com/nginx-ingress-controller/configuration/virtualserver-and-virtualserverroute-resources/#addheader for VS/VSR